All five were passengers in a Liberty Helicopters aircraft when it crashed into the East River around sunset on Sunday. The pilot, Richard Vance, 33, was the only person to survive the crash.

Liberty Helicopters describes itself as “the largest and most experienced helicopter sightseeing and charter service in New York City,” with a fleet of 10 Airbus helicopters. Sunday’s deadly incident was the third time in 11 years one of its helicopters crashed in New York.

New York’s U.S. Sen. Chuck Schumer has said federal regulators should temporarily halt flights by the owner of the helicopter. The Democrat is calling on the Federal Aviation Administration to suspend Liberty Helicopters’ operating license until the facts of the crash are known. The FAA hasn’t commented on Schumer’s suggestion.

The National Transportation Safety Board is investigating the cause of the crash.

NTSB member Bella Dinh-Zarr said Monday said the helicopter’s floats inflated, but investigators will look at whether they deployed properly. She added that it will be some time before the cause is determined.

A federal official told The Associated Press the pilot told authorities he believed a passenger’s bag might have hit an emergency fuel shutoff switch. The official was briefed on the investigation but was not authorized to speak publicly about it and spoke Monday on condition of anonymity.